Curious if I can get a sanity check off my problem diagnosis (or alternate theories!)
I tried a long print today and wound up with a 1/2 inch layer shift on the x-axis near the end of a long print, taller than most I've done, not certainly not the tallest.
It occured on a spool I just opened a few days ago and printed two other ~250g pieces with. I'm very certain that I never lost control of the filament end. My spool in mounted using the stock ender 3 mount on the left side is the gantry and a filament guide arm.
After reading a bit, I'm thinking this was due to the filament on the spool loosening up from a large travel and then binding on itself. Seems the easiest way to fix this might just be to put more space between the spool and the printer so the slack can absorb the shifting without pushing back on the spool and loosening several turns off filament.
I don't think it's heat or any general axis binding as the shift only happened at a single layer, at a hight that I've been able to print through before, and the motion generally appears smooth when I exercise it.
So... Experimentation will probably prove me right or wrong, but before I sink another day of print time... Does that sound reasonable or am I missing a common problem?
Edit: Solved, see comment by @Vathsade@lemmy.ca for the actual problem. Many thanks to all who provided their thoughts!
My initial guess (having had similar layer shifts in the past) is that one of those skinny 'Y' vertical pieces with angled overhangs simply curled up a little too much (shrinking warpage) and eventually the nozzle took a path where it made contact with the raised edge and cause the motor/belt to slip until it continued in the new position.
Ways to prevent include much higher cooling for those curling points (super slow high fan), or enclosure of the entire unit to mitigate warping.
Sorry for late response, hope it helps or you solved it.
Winner winner chicken dinner! This is EXACTLY what happened. I reprinted again after tightening belts, fixing bed wobble, and re-leveling, and kept a closer eye on it this time. The nozzle was indeed catching on that "Y" support due to the edge curling up. Wasnt enough to kill the print this time, but enough to make me nervous...
Ironically, the thing I'm printing is an all-in-one case so that I can segregate the PSU, main board, pi, and controls from the printer itself to enclose it and have better temp control!